Simultaneous determination and pharmacokinetic study of stachydrine and leonurine in rat plasma after oral administration of Herba Leonuri extract by LC-MS/MS.

A simple, sensitive and specific method was developed for simultaneous determination of stachydrine and leonurine in rat plasma using diphenhydramine as an internal standard (IS). The separation was performed on an Agilent ZORBAX Eclipse XDB-C(18) column (150mm×4.6mm, i.d., 5μm) at a flow rate of 0.6mL/min, and the mixture of methanol-water containing 0.1% formic acid was used as the mobile phase. The lower limits of quantitation (LLOQs) in rat plasma were 0.895 and 0.287ng/mL for stachydrine and leonurine, respectively. Intra- and inter-day precisions were within 14.4% and accuracies were not more than 3.0%. After single oral administration of 14.5g/kg Herba Leonuri extract, C(max) of stachydrine and leonurine in rat plasma were respectively 1608±267 and 43.3±8.2ng/mL, while T(max) values were respectively 0.75±0.27 and 0.83±0.26h. The results demonstrated that the present LC-MS/MS method was sensitive enough for pharmacokinetic study of stachydrine and leonurine following oral administration of Herba Leonuri extract.